SDL_offscreenwindow.c: swap include order of SDL_egl_c.h/SDL_sysvideo.h

Fixes redefinition warnings from windows builds.
Reference issue: https://github.com/libsdl-org/SDL/issues/6239
(cherry picked from commit d86cb8ec9ef83e48f99c644d127373cf60a67046)

src/video/offscreen/SDL_offscreenwindow.c

@@ -23,8 +23,8 @@
 
 #if SDL_VIDEO_DRIVER_OFFSCREEN
 
-#include "../SDL_egl_c.h"
 #include "../SDL_sysvideo.h"
+#include "../SDL_egl_c.h"
 
 #include "SDL_offscreenwindow.h"